In the operation of a burner to carry out combustion, especially in an industrial setting, a major problem is heat damage to the burner.
One conventional method for reducing heat damage to a burner is to circulate a coolant such as water through the burner. While this method provides adequate cooling to the burner, it has several disadvantages. A supply of clean water is required at the requisite pressure and such a supply may not always be readily available without considerable effort and additional equipment. The burner design itself is considerably more complicated to accommodate the coolant passages. The cooled burner surface temperature may be low enough to cause condensation of furnace gases which may corrode the burner. Coolant leaks may develop within the burner which can cause damage to the burner or a shutdown of the combustion operation.
For all of these reasons it is desirable to have a burner and combustion method which can operate without the need for employing circulating coolant.
One method for addressing this problem which has found use in industrial combustion operations comprises recessing the burner from the furnace or combustion zone. Generally such a burner is recessed within a cavity in the furnace wall. In this way less heat or energy from the combustion zone is radiated to the burner surface and thus a separate coolant is not needed. Heat transfer by radiation from the furnace decreases as the burner is withdrawn into the cavity. However, with a burner recessed within a cavity, combustion may, and usually does, occur within the cavity thus generating heat close to the burner surface and thereby increasing the heat to the burner.
With air as the oxidant there is a large volume of oxidant flow which can be used to cool the burner and refractory walls. Moreover, the flame temperature for combustion with air is lower than that for combustion with oxygen or oxygen-enriched air so that combustion within the cavity usually does not have serious consequences. However the problem of heat damage to a recessed burner by combustion within a cavity becomes more acute as the oxygen concentration of the oxidant is increased to concentrations significantly greater than that of air. Accordingly, in such situations a burner is recessed only a small distance from the combustion zone thus reducing the protective effect of the recession, and/or the flowrates of fuel and oxidant are very carefully controlled to diminish combustion proximate the burner which serves to complicate the combustion operation and to reduce its efficiency.
Accordingly it is an object of this invention to provide a combustion method which can operate efficiently without the need for water cooling.
It is a further object of this invention to provide a burner which can operate without damage caused by heat and without the need for water cooling
It is yet another object of this invention to provide a combustion method employing oxygen or oxygen-enriched air as the oxidant which can be carried out without the need for water cooling.
It is a still further object of this invention to provide a burner which can use oxygen or oxygen-enriched air as the oxidant while not requiring water cooling.